feat: improve URI recognition (#1736)

feat: improve URI recognition (#1736)

* Improve origin URI recognition

- Consolidate a number of separate ad hoc tests for recognising URIs into Alire.URI.URI_Kind
- Add support for origin URLs with scheme "ssh://"
- Add bitbucket.org to the list of hosts recognised as git only
- Treat ".git/" suffix the same as ".git"
- Change publish command to raise errors on URLs with "file:" scheme (sidestepping a bug where the whole URL was treated as a relative path)
- Change various error messages
- Change handling of some obscure edge cases

* Fix source archives hosted on GitHub or similar

* Fix test when ssh command is unavailable

* Workaround for GNAT 10 bug

* Further improve URI recognition

* Fix existing test

* Add test for local indexes

* Add test for 'clean --cache' command

* Fix on Windows

* Fix on MacOS

* Clean up local-index-not-found test

* Consolidate 'Host' implementations

* Fix Fragment for local URLs

* Fix test

* Improve publishing test

* Fix documentation

* Remove redundant test

* Fix tests

* Fix typos

* Switch to US English

* Use crate_dirname

* Use less fragile test for git failure

* Add clarifying comments

* Treat http with non-empty userinfo as private

* Fix typo